Electric spark ignition apparatus



Sept. 6, 1955 J. A. LAIRD 2,717,337

ELECTRIC SPARK IGNITION APPARATUS Filed April 8, 1952 United States Patent ELECTRIC SPARK IGNITION APPARATUS John Andrew Laird, Coventry, England, assignor to lJosflph Lucas (Industries) Limited, Birmingham, Eng- Application April 8, 1952, Serial No. 281,116

Claims priority, application Great Britain April 9, 1951 6 Claims. (Cl. 315-243) This invention relates to electric spark ignition apparatus for igniting combustible gas mixtures in prime movers, the apparatus being of the kind comprising a condenser, and a control gap and inductance in series with the condenser, the latter receiving its charge from any convenient source, and the discharge being effected across an igniting plug.

The object of the invention is to minimise risk of failure of a spark occurring at the igniting plug.

The invention comprises an apparatus of the kind aforesaid having combined with it an additional condenser arranged in parallel with the control gap and at least a part of the inductance.

Alternatively the additional condenser is connected in series with an inductance which is coupled to the inductance associated with the control gap.

In the accompanying drawings:

Figures 1, 2 and 3 are diagrams respectively illustrating three embodiments of the invention.

The already known part of a system embodying the invention, comprises a condenser a of the desired capacity. This condenser is intended to be charged intermittently from a magneto, ignition coil or any other convenient source. It is not essential to the invention. that the condenser a shall be a separately formed component, as the self-capacity of the source or the distributedcapacity of the cables or associated parts of the system may be sufficient for the purpose in view and we desire it to be understood that the term condenser as used herein shall include any sufficient capacity which is in herently associated with the system.

In series with the condenser is arranged a control gap b and also an inductance 0 adapted to prolong the discharge from the condenser, the control gap being adapts i to break down when the condenser voltage reaches an amount determined by the gap. With discharge of the condenser across the control gap, a simultaneous discharge normally occurs across the ignition gap d. In some conditions, however, the discharge across the i nition gap may fail, and the risk of this possibility is obviated or minimised in the following manner.

According to the present invention, there is arranged in parallel with the control gap and inductance, an additional condenser e as shown in Figure l. The capacity of the additional condenser may have a widely variable value, the optimum value for a given system being readily ascertainable by experiment. Also, if desired a high resistance 1 may be provided in the position shown, or across the igniting gap, where the normal leakage across Patented Sept. 6, 1955 the insulation of the igniting gap is insufficient to serve the same purpose.

Whilst the desired result may be ensured by arranging the additional condenser in the manner above described, it is preferred to introduce a step-up transformer effect. This may be obtained by connecting one side of the additional condenser e to any convenient point of the inductance 0, so as to obtain an autotransformer effect as shown in Figure 2. Or alternatively an additional inductance g coupled to the said inductance c may be connected in series with the additional condenser e to obtain the desired step-up transformer etfect as shown in Figure 3.

In any of the above described means, the inductance may be arranged as shown, or it may be placed between the condenser a and the control gap.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. Electric spark gap ignition apparatus for the purpose specified comprising a discharge circuit including capacity, a control gap in said circuit adapted to control the discharge and an inductance in series with said capacity, and a condenser connected in parallel with the said control gap and at least a part of the inductance.

2. Electric spark gap ignition apparatus for the purpose specified comprising a discharge circuit including a condenser, a control gap in said circuit adapted to control the discharge and an inductance in series with said condenser, and a second condenser connected in parallel with the said control gap and at least a part of the inductance.

3. Electric spark gap ignition apparatus for the purpose specified comprising a discharge circuit including capacity, a control gap in said circuit adapted to control the disharge, an inductance associated with said control gap, a second inductance coupled to said first inductance,

and a condenser arranged in parallel with the control gap, one side of said condenser being connected in series with the said second inductance.

4. Electric spark gap ignition apparatus for the purpose specified comprising a discharge circuit including a condenser, a control gap adapted to control the discharge, an inductance associated with said control gap, a second inductance coupled to said first inductance, and a second condenser arranged in parallel with the control gap, one side of said condenser being connected in series with the said second inductance.

5. Electric spark ignition apparatus for the purpose specified, comprising a discharge circuit including capacity, a control gap in said circuit to control the discharge, an inductance in series with said capacity, and a condenser connected in parallel with said control gap.

6. Electric spark ignition apparatus for the purpose specified, comprising a discharge circuit including a condenser, a control gap in said circuit to control the discharge, an inductance in series with said condenser, and a second condenser connected in parallel with said con trol gap.

References Cited in the file of this patent UNSTED STATES PATENTS 2,433,462 Laird Dec. 30, 1947 

